Project Summary Environmental exposures play a leading role in the development of human disease and are therefore of significant interest, but measuring the myriad of environmental exposures encountered over a lifetime is an immense challenge. Even more complicated is identifying the molecular pathways disrupted by each environmental exposure encountered. Yet, progress on both of these challenges is ultimately fundamental to understanding the contribution of the environment to human health. The overarching mission of my research program is to address this critical need by developing and applying novel metabolomic technologies. Metabolomics is a relatively new analytical approach that is ideally suited to help address these formidable challenges because it comprehensively profiles small molecules of both exogenous and endogenous origin. In practice, however, metabolomics has not fulfilled its potential in the environmental health sciences. Its application has been severely limited due to the tens of thousands of signals detected by liquid chromatography/mass spectrometry (LC/MS) that cannot be identified. Without biochemically naming the metabolomic signals, biological inference is compromised and insights into exposure chemicals or effect mechanisms are prevented. The major goal of my research program is to overcome this barrier in metabolomics to (1) enable unprecedented exposure analysis in humans and (2) to discover toxicant effect mechanisms by using zebrafish. First, with new technologies that my laboratory has developed, we will name each signal detected by LC/MS untargeted metabolomics from human blood and the zebrafish embryo. This will constitute the human and zebrafish ?reference metabolomes?. We will then develop a resource to automate identification and quantitation of each metabolite in the reference metabolomes. Second, we will screen the zebrafish reference metabolome to identify effect mechanisms of specific toxicants known to have adverse effects on only a single zebrafish organ. We will test our hypothesis that each organ?s metabolism is similarly disrupted by some toxicants, but that their unique phenotypic responses reflect organ-specific sensitivities to particular pathways. Thus, in addition to building a metabolomics resource that will greatly enhance exposure analysis in human subjects, we also expect that the application of our platform to zebrafish will identify toxicant effect mechanisms and establish biochemical pathways that contribute to particular phenotypes.